CASE STUDY - Prospective Sealine 34 owner
Challenge
MBS was commissioned by a prospective vendor to Pre-Purchase survey a Sealine 34. Whilst everything appeared in decent condition topsides, and at face value on the Volvo engines; and during the river trial when the engines were tested extensively. It was noted on the "lift out and hold" the hull had over 25 - 30% of its surface area covered in gelcoat  blisters caused by osmosis. The vessel was 23 years old. The starboard side had 2/3 rds more surface blisters (up to 3mm deep) than the port side. The blisters were tested and found to be Strength 3 PH acidic solution, and equally gave off a vinegar smell which gave cause for concern.
Solution

The client was advised to seek out professional guidance from a GRP specialist on these matters and a job quote was received for a significant 5 figure sum to repair the vessel's underwater gelcoat and rovings.
Survey Benefit

The client realised very quickly that he was going to be seriously out of pocket and in consultation with his partner declined NOT to pursue the vessel any further. Therefore, the sale did not go ahead as planned.
 
This is a clear example of a Boat Surveyor adding value to the buying process and saving the client from taking on what could have been a huge financial and operational liability.

CASE STUDY VIDEO
Stern drive gearbox oil emulsification issue that led to client withdrawing his interest in acquiring the sports cruiser petrol engined craft.

CASE STUDY Two Pack epoxy paint process
Blacking versus Two Pack ?
 

Blacking Most Narrowboats owners choose to use bitumen based blacking paints; its cheap to acquire, apply without specialist help needed and relatively quick drying times. Most yards will allow its application to the craft. The downside is that if not adhered properly to the base metal it peels and turns scabrous within 12 to 18 months of 1st application once it experiences and undergoes abrading forces when say entering locks, berthing, drydocking, lying alongside other narrowboats, etc. 

Two Pack Epoxy Paints
This surveyors preference would be to spray two pack epoxy paints (Epifane, International, Hempel, Jotun, etc) rather than single pack paints which are commonly used on Narrowboats. They offer a number of distinct advantages.

When two pack paint has cured it is harder than single pack paint and tends to resist fuel, acid rain, sunlight (ultra violet light) etc. much better than single pack paints; which oxidises and becomes dull over a longer period. It has been known to develop a milky haze.

Two pack paints consists of different resins, made of acrylic and melamine (therefore, its proper title is Two Pack Acrylic Enamel). When you mix your paint, you add a second resin, or hardener, called Poly-isocyanate Resin.
At this stage a chemical reaction takes place between the two resins which makes them harden. This eliminates the common problem of Micro blistering. Micro blistering is caused by moisture being trapped between various layers of paint. As two pack paints use a chemical drying process rather than an air drying process; micro blistering is not a problem that will occur.

As long as temperatures are above 10 degrees celsius one can create ideal conditions to achieve the perfect paint finish.

Footnote: Try to resist the short cut offered by Ballistic paints who claim you can paint over blacking directly with their Two pack epoxy offering. I've spoken to a number of narrowboat owners who have tried it and the result was "disappointing and below expectations".